Producing polyolefin products

ABSTRACT

A method of polymerizing olefins is disclosed. The method comprises contacting ethylene and at least one comonomer with a catalyst system to produce a polyolefin polymer that is multimodal. The catalyst system comprises a first catalyst that promotes polymerization of the ethylene into a low molecular weight (LMW) portion of the polyolefin polymer and a second catalyst that promotes polymerization of the ethylene into a high molecular weight (HMW) portion of the polyolefin polymer. The first catalyst and at least a portion of the second catalyst are co-supported to form a commonly-supported catalyst system and at least a portion of the second catalyst is added as a catalyst trim feed to the catalyst system.

RELATED APPLICATIONS

This application is a National Stage Application under 35 U.S.C. § 371of International Application Number PCT/US2015/015141, filed Feb. 10,2015 and published as WO 2015/123177 on Aug. 20, 2015, which claims thebenefit to the following U.S. Provisional Applications 61/938,472, filedFeb. 11, 2014; 61/938,466, filed Feb. 11, 2014; 61/981,291, filed Apr.18, 2014; 61/985,151, filed Apr. 28, 2014; 62/032,383, filed Aug. 1,2014; 62/088,196, filed Dec. 5, 2014; 62/087,914, filed Dec. 5, 2014;62/087,911, filed Dec. 5, 2014; 62/087,905, filed Dec. 5, 2014; theentire contents of which are incorporated herein by reference in itsentirety.

BACKGROUND

Ethylene alpha-olefin (polyethylene) copolymers are typically producedin a low pressure reactor, utilizing, for example, solution, slurry, orgas phase polymerization processes. Polymerization takes place in thepresence of catalyst systems such as those employing, for example, aZiegler-Natta catalyst, a chromium based catalyst, a metallocenecatalyst, or combinations thereof.

A number of catalyst compositions containing single site, e.g.,metallocene, catalysts have been used to prepare polyethylenecopolymers, producing relatively homogeneous copolymers at goodpolymerization rates. In contrast to traditional Ziegler-Natta catalystcompositions, single site catalyst compositions, such as metallocenecatalysts, are catalytic compounds in which each catalyst moleculecontains one or only a few polymerization sites. Single site catalystsoften produce polyethylene copolymers that have a narrow molecularweight distribution. Although there are single site catalysts that canproduce broader molecular weight distributions, these catalysts oftenshow a narrowing of the molecular weight distribution (MWD) as thereaction temperature is increased, for example, to increase productionrates. Further, a single site catalyst will often incorporate comonomeramong the molecules of the polyethylene copolymer at a relativelyuniform rate.

It is generally known in the art that a polyolefin's MWD will affect thedifferent product attributes. Polymers having a broad molecular weightdistribution may have improved physical properties, such as stiffness,toughness, processability, and environmental stress crack resistance(ESCR), among others. To achieve these properties, bimodal polymers havebecome increasingly important in the polyolefins industry, with avariety of manufacturers offering products of this type. Whereas oldertechnology relied on two-reactor systems to generate such material,advances in catalyst design and supporting technology have allowed forthe development of single-reactor bimetallic catalyst systems capable ofproducing bimodal high density polyethylene (HDPE). These systems areattractive both from a cost perspective and ease of use.

The composition distribution of an ethylene alpha-olefin copolymerrefers to the distribution of comonomer, which form short chainbranches, among the molecules that comprise the polyethylene polymer.When the amount of short chain branches varies among the polyethylenemolecules, the resin is said to have a “broad” composition distribution.When the amount of comonomer per 1000 carbons is similar among thepolyethylene molecules of different chain lengths, the compositiondistribution is said to be “narrow”.

The composition distribution is known to influence the properties ofcopolymers, for example, stiffness, toughness, extractable content,environmental stress crack resistance, and heat sealing, among otherproperties. The composition distribution of a polyolefin may be readilymeasured by methods known in the art, for example, Temperature RaisingElution Fractionation (TREF) or Crystallization Analysis Fractionation(CRYSTAF).

It is generally known in the art that a polyolefin's compositiondistribution is largely dictated by the type of catalyst used and istypically invariable for a given catalyst system. Ziegler-Nattacatalysts and chromium based catalysts produce resins with broadcomposition distributions (BCD), whereas metallocene catalysts normallyproduce resins with narrow composition distributions (NCD).

Resins having a broad orthogonal composition distribution (BOCD) inwhich the comonomer is incorporated predominantly in the high molecularweight chains can lead to improved physical properties, for exampletoughness properties and environmental stress crack resistance (ESCR).Because of the improved physical properties of resins with orthogonalcomposition distributions needed for commercially desirable products,there exists a need for controlled techniques for forming polyethylenecopolymers having a broad orthogonal composition distribution.

Control of these properties is obtained for the most part by the choiceof the catalyst system. Thus, the catalyst design is important forproducing polymers that are attractive from a commercial standpoint.Because of the improved physical properties of polymers with the broadmolecular distributions needed for commercially desirable products,there exists a need for controlled techniques for forming polyethylenecopolymers having a broad molecular weight distribution.

SUMMARY

A method of polymerizing olefins is disclosed. The method comprisescontacting ethylene and at least one comonomer with a catalyst system toproduce a polyolefin polymer that is multimodal. The catalyst systemcomprises a first catalyst that promotes polymerization of the ethyleneinto a low molecular weight (LMW) portion of the polyolefin polymer anda second catalyst that promotes polymerization of the ethylene into ahigh molecular weight (HMW) portion of the polyolefin polymer. The firstcatalyst and at least a portion of the second catalyst are co-supportedto form a commonly-supported catalyst system and at least a portion ofthe second catalyst is added as a catalyst trim feed to the catalystsystem. Polymers made by the methods herein are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative plot of molecular weight distribution ofpolyolefin polymerized with a two catalyst system that includes a firstmetallocene catalyst and a second metallocene catalyst, in accordancewith embodiments described herein.

FIG. 2 is a schematic of a gas-phase reactor system, showing theaddition of at least two catalysts, at least one of which is added as atrim catalyst in accordance with embodiments described herein.

FIG. 3 is an exemplary bar chart depicting gel data of polyethylenepolymerized via different catalyst systems processed on two differentextruders.

DETAILED DESCRIPTION

The melt flow ratio (MFR) of a polyethylene is the ratio of meltindexes, I₂₁/I₂, and is an important property to be able to control inpolymerization methods. In polymerization methods using multiplecatalysts, such as a dual catalyst system comprising a HMW catalystspecies and a LMW catalyst species, it is known that MFR may becontrolled using trim addition of the LMW catalyst species.

The methods disclosed herein utilize a commonly-supported catalystsystem with trim addition of the HMW catalyst species, rather than theLMW catalyst species. Specifically, the methods comprise contactingethylene and at least one comonomer with a catalyst system to produce apolyolefin polymer that is multimodal. The catalyst system comprises afirst catalyst that promotes polymerization of the ethylene into a lowmolecular weight (LMW) portion of the polyolefin polymer and a secondcatalyst that promotes polymerization of the ethylene into a highmolecular weight (HMW) portion of the polyolefin polymer. The firstcatalyst and at least a portion of the second catalyst are co-supportedto form a commonly-supported catalyst system and at least a portion ofthe second catalyst is added as a catalyst trim feed to the catalystsystem.

The catalyst system useful in these methods may be formulated with ahigher than typically desired amount of LMW catalyst species, and thenMFR may be controlled via trim addition of additional HMW catalystspecies. It is believed that the methods disclosed herein facilitatebetter mixing of the polymer LMW and HMW fractions being polymerized,and thus they surprisingly result in a reduction in polymer gels.Moreover, without wishing to be bound by theory, it is believed thatwhen the HMW catalyst species is used as the trim catalyst, a HMWpolymer shell may beneficially form on the polymer particle, which mayimprove extrusion properties and contribute to the reduction in gels.Exemplary data demonstrating these effects is provided herein.

Herein, the modifiers “LMW” and “HMW” of “LMW catalyst species” and “HMWcatalyst species,” respectively, refer to the contribution of thecatalyst to the polymer molecular weight in polymerization, and do notrefer to the molecular weight of the catalysts themselves.

The methods disclosed herein may be used with a variety of differentcatalysts. A useful HMW catalyst species may comprisebis(n-propylcyclopentadienyl) Hafnium dimethyl, referred to herein as“HfP” for convenience. A useful LMW catalyst species may comprise mesoand/or rac entantiomers of di(1-ethylindenyl) zirconium dimethyl,referred to herein as “EthInd” or “1 EtInd2ZrMe2” for convenience. Thus,in the methods herein, the first catalyst may be a LMW catalyst speciessuch as EthInd in a slurry or other form, driving polymerization of aLMW fraction or portion of the polyethylene polymer. The second catalystmay be a HMW catalyst species such as HfP in a solution or other form,driving polymerization of the HMW fraction or portion of thepolyethylene polymer. At least a portion of the second catalyst or HMWcatalyst species is co-deposited on a support prior to entering thereactor, with additional HMW catalyst species added as trim to controlMFR and/or other properties of the polymer.

As indicated, the two catalysts may be co-supported on a catalystsupport to form a commonly supported catalyst system prior to flowingthe catalyst to the polymerization reactor. The catalysts may beco-supported on a single common support or co-supported on multiplecommon supports. Additionally, the catalysts and methods disclosedherein may be used with a variety of reactor arrangements, for example,single-reactor or multiple-reactor polymerization systems.

The commonly supported catalyst system may be characterized by aninitial co-deposit on a mol fraction basis of the second catalyst to thefirst catalyst. As used herein, “initial co-deposit on a mol fractionbasis of the second catalyst to the first catalyst” refers to therelative amounts of the second catalyst and the first catalyst that areinitially co-deposited on the common support. For example, an initialco-deposit on a mol fraction basis of the second catalyst to the firstcatalyst of 0.6:0.4 means that 0.6 mol of second catalyst areco-deposited on the common support for every 0.4 mol of first catalystdeposited on the common support. The initial co-deposit on a molfraction basis of the second catalyst to the first catalyst may rangefrom, for example, 0.01:0.99 to 0.99:0.01, 0.1:0.9 to 0.9:0.1, 0.2:0.8to 0.8:0.2, 0.7:0.3 to 0.3:0.7, 0.4:0.6 to 0.6:0.4, or 0.55:0.45 to0.45:0.55, or be about 0.6:0.4 or about 0.5:0.5.

The amount of additional HMW catalyst species that may be added as trimper gram of the dry co-supported catalyst (i.e. the weight of catalystprior to being slurried) may range from 1.8 μmol to 150 μmol, 3.6 μmolto 120 μmol, 6.2 μmol to 90 μmol, 12.4 μmol to 75 μmol, or 25 μmol to 50μmol.

The methods disclosed herein may enable the formation of polymers withan improved balance of properties, such as stiffness, toughness,processability, and environmental stress crack resistance. Such abalance of properties can be achieved, for example, by controlling theamounts and types of catalysts present on the support. Selection of thecatalysts and ratios may be used to adjust the MWD of the polymerproduced. The MWD can be controlled by combining catalysts giving thedesired weight average molecular weight (MW) and individual molecularweight distributions of the produced polymer. For example, a typical MWDfor linear metallocene polymers is 2.5 to 3.5. Blend studies indicate itwould be desirable to broaden this distribution by employing mixtures ofcatalysts that each provide different average molecular weights. In suchcases, the ratio of the weight average molecular weight or the numberaverage molecular weight for a low molecular weight component of thepolymer and a high molecular weight component of the polymer could bebetween 1:1 and 1:10, or about 1:2 and 1:5, for instance.

Appropriate selection of the catalysts and ratios may be used to adjustnot just the MWD, but also the short chain branch distribution (SCBD)and long-chain branch distribution (LCBD) of the polymer, for example,to provide a polymer with a broad orthogonal composition distribution(BOCD). The MWD, SCBD, and LCBDs would be controlled by combiningcatalysts with the appropriate weight average MW, comonomerincorporation, and long chain branching (LCB) formation under theconditions of the polymerization.

The density of a polyethylene copolymer provides an indication of theincorporation of comonomer into a polymer, with lower densitiesindicating higher incorporation. The difference in the densities of theLMW component and the HMW component may be greater than about 0.02g/cm3, or greater than about 0.04 g/cm3, with the HMW component having alower density than the LMW component. These factors can be adjusted bycontrolling the MWD and SCBD, which, in turn, can be adjusted bychanging the relative amounts of the pre-catalysts on the support. Thismay be adjusted during the formation of the pre-catalysts or by addingone of the components as trim. Feedback of polymer property data can beused to adjust the amount of catalyst added as trim.

Further, a variety of resins with different MWD, SCBD, and LCBD may beprepared from a limited number of catalysts. To perform this function,the pre-catalysts should trim well onto activator supports. Twoparameters that benefit this are solubility in alkane solvents and rapidsupportation on the catalyst slurry en-route to the reactor. This favorsthe use of MCNs to achieve controlled MWD, SCBD, and LCBD. Techniquesfor selecting catalysts that can be used to generate targeted molecularweight compositions, including BOCD polymer systems, are disclosedherein.

FIG. 1 is a plot 100 of molecular weight distributions for a polyolefinpolymer produced by a two catalyst system that includes first and secondcatalysts, in accordance with embodiments described herein. In the plot100, the x-axis 102 represents the log of the MW, and the y-axis 104represents the MWD. Each of the catalysts can be selected to contributea certain molecular weight component. For example, a catalyst, such asEthInd, the meso and rac entantiomers of which are shown as structures(I-A) and (I-B) respectively below, may be selected to produce a lowmolecular weight component 106. Another catalyst, such as HfP, shown asstructure (II) below, may be selected to produce a higher molecularweight component 108. In one or more embodiments, catalysts such asthose shown in structures (IV-C), (IV-D), (V-A), and (V-B) may beutilized. Of course, other metallocene catalysts or non-metallocenecatalysts, as described herein, may be selected, a few of which are alsoshown below. The individual molecular weight components form a singleMWD curve 110 for the polymer. The particular metallocene ornon-metallocene catalysts selected may depend on the desired downstreamapplications of the formed polymer resins, such as for film,blow-molding applications, pipe applications, and so on.

The polymer produced may include polyethylene that is multimodal. Forexample, the polyethylene may be bimodal and have chains formed via apolymerization catalyst system having a low molecular weight (LMW)species catalyst and a high molecular weight (HMW) species catalyst thatare co-supported to give a commonly supported catalyst system, andwherein at least a portion of the HMW species catalyst is a catalysttrim. In some instances, the polyethylene is a copolymer of ethylene andan alpha olefin comonomer having from 4 to 20 carbon atoms.

Various catalyst systems and components may be used to generate thepolymers and molecular weight compositions disclosed. These arediscussed in the sections to follow. The first section discussescatalyst compounds that can be used in embodiments. The second sectiondiscusses generating catalyst slurries that may be used for implementingthe techniques described. The third section discusses catalyst supportsthat may be used. The fourth section discusses catalyst activators thatmay be used. The fifth section discusses the catalyst componentsolutions that may be used to add additional catalysts in trim systems.Gas phase polymerizations may use static control or continuity agents,which are discussed in the sixth section. A gas-phase polymerizationreactor with a trim feed system is discussed in the seventh section. Theuse of the catalyst composition to control product properties isdiscussed in an eighth section and an exemplary polymerization processis discussed in a ninth section. Examples of the implementation of theprocedures discussed are incorporated into a tenth section.

Catalyst Compounds

Metallocene Catalyst Compounds

Metallocene catalyst compounds may be used in the methods herein.Metallocene catalyst compounds include “half sandwich” and/or “fullsandwich” compounds having one or more Cp ligands (cyclopentadienyl andligands isolobal to cyclopentadienyl) bound to at least one Group 3 toGroup 12 metal atom, and one or more leaving group(s) bound to the atleast one metal atom. As used herein, all reference to the PeriodicTable of the Elements and groups thereof is to the NEW NOTATIONpublished in HAWLEY'S CONDENSED CHEMICAL DICTIONARY, Thirteenth Edition,John Wiley & Sons, Inc., (1997) (reproduced there with permission fromIUPAC), unless reference is made to the Previous IUPAC form noted withRoman numerals (also appearing in the same), or unless otherwise noted.

The Cp ligands are one or more rings or ring system(s), at least aportion of which includes π-bonded systems, such as cycloalkadienylligands and heterocyclic analogues. The ring(s) or ring system(s)typically include atoms selected from the group consisting of Groups 13to 16 atoms, and, in a particular exemplary embodiment, the atoms thatmake up the Cp ligands are selected from the group consisting of carbon,nitrogen, oxygen, silicon, sulfur, phosphorous, germanium, boron,aluminum, and combinations thereof, where carbon makes up at least 50%of the ring members. In a more particular exemplary embodiment, the Cpligand(s) are selected from the group consisting of substituted andunsubstituted cyclopentadienyl ligands and ligands isolobal tocyclopentadienyl, non-limiting examples of which includecyclopentadienyl, indenyl, fluorenyl and other structures. Furthernon-limiting examples of such ligands include cyclopentadienyl,cyclopentaphenanthreneyl, indenyl, benzindenyl, fluorenyl,octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene,phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl,8-H-cyclopent[a]acenaphthylenyl, 7-H-dibenzofluorenyl,indeno[1,2-9]anthrene, thiophenoindenyl, thiophenofluorenyl,hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or “H4Ind”), substituted versions thereof (as discussed and described in moredetail below), and heterocyclic versions thereof.

The metal atom “M” of the metallocene catalyst compound can be selectedfrom the group consisting of Groups 3 through 12 atoms and lanthanideGroup atoms; selected from the group consisting of Groups 3 through 10atoms; selected from the group consisting of Sc, Ti, Zr, Hf, V, Nb, Ta,Mn, Re, Fe, Ru, Os, Co, Rh, Ir, and Ni; selected from the groupconsisting of Groups 4, 5, and 6 atoms; selected from the groupconsisting of Ti, Zr, Hf atoms; and selected from Zr or Hf. Theoxidation state of the metal atom “M” can range from 0 to +7 in oneexemplary embodiment; and in a more particular exemplary embodiment, canbe +1, +2, +3, +4, or +5; and in yet a more particular exemplaryembodiment can be +2, +3 or +4. The groups bound to the metal atom “M”are such that the compounds described below in the formulas andstructures are electrically neutral, unless otherwise indicated. The Cpligand forms at least one chemical bond with the metal atom M to formthe “metallocene catalyst compound.” The Cp ligands are distinct fromthe leaving groups bound to the catalyst compound in that they are nothighly susceptible to substitution/abstraction reactions.

The one or more metallocene catalyst compounds can be represented by thestructure (VI):Cp^(A)Cp^(B)MX_(n),in which M is as described above; each X is chemically bonded to M; eachCp group is chemically bonded to M; and n is 0 or an integer from 1 to4, and either 1 or 2 in a particular exemplary embodiment.

The ligands represented by Cp^(A) and Cp^(B) in structure (VI) can bethe same or different cyclopentadienyl ligands or ligands isolobal tocyclopentadienyl, either or both of which can contain heteroatoms andeither or both of which can be substituted by a group R. In at least onespecific embodiment, Cp^(A) and Cp^(B) are independently selected fromthe group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl,fluorenyl, and substituted derivatives of each.

Independently, each Cp^(A) and Cp^(B) of structure (VI) can beunsubstituted or substituted with any one or combination of substituentgroups R. Non-limiting examples of substituent groups R as used instructure (VI) as well as ring substituents in structures discussed anddescribed below, include groups selected from the group consisting ofhydrogen radicals, alkyls, alkenyls, alkynyls, cycloalkyls, aryls,acyls, aroyls, alkoxys, aryloxys, alkylthiols, dialkylamines,alkylamidos, alkoxycarbonyls, aryloxycarbonyls, carbamoyls, alkyl- anddialkyl-carbamoyls, acyloxys, acylaminos, aroylaminos, and combinationsthereof. More particular non-limiting examples of alkyl substituents Rassociated with structures herein include methyl, ethyl, propyl, butyl,pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl, phenyl, methylphenyl,and tert-butylphenyl groups and the like, including all their isomers,for example, tertiary-butyl, isopropyl, and the like.

As used herein, and in the claims, hydrocarbyl substituents, or groups,are made up of between 1 and 100 or more carbon atoms, the remainderbeing hydrogen. Non-limiting examples of hydrocarbyl substituentsinclude linear or branched or cyclic: alkyl radicals; alkenyl radicals;alkynyl radicals; cycloalkyl radicals; aryl radicals; alkylene radicals,or a combination thereof. Non-limiting examples include methyl, ethyl,propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl; olefinicallyunsaturated substituents including vinyl-terminated ligands (for examplebut-3-enyl, prop-2-enyl, hex-5-enyl and the like), benzyl or phenylgroups and the like, including all their isomers, for example tertiarybutyl, isopropyl, and the like.

As used herein, and in the claims, substituted hydrocarbyl substituents,or groups, are made up of between 1 and 100 or more carbon atoms, theremainder being hydrogen, fluorine, chlorine, bromine, iodine, oxygen,sulfur, nitrogen, phosphorous, boron, silicon, germanium or tin atoms orother atom systems tolerant of olefin polymerization systems.Substituted hydrocarbyl substituents are carbon based radicals.Non-limiting examples of substituted hydrocarbyl substituentstrifluoromethyl radical, trimethylsilanemethyl (Me3SiCH 2-) radicals.

As used herein, and in the claims, heteroatom substituents, or groups,are fluorine, chlorine, bromine, iodine, oxygen, sulfur, nitrogen,phosphorous, boron, silicon, germanium or tin based radicals. They maybe the heteroatom atom by itself. Further, heteroatom substituentsinclude organometalloid radicals. Non-limiting examples of heteroatomsubstituents include chloro radicals, fluoro radicals, methoxy radicals,diphenyl amino radicals, thioalkyls, thioalkenyls, trimethylsilylradicals, dimethyl aluminum radicals, alkoxydihydrocarbylsilyl radicals,siloxydiydrocabylsilyl radicals, tris(perflourophenyl)boron and thelike.

Other possible radicals include substituted alkyls and aryls such as,for example, fluoromethyl, fluroethyl, difluroethyl, iodopropyl,bromohexyl, chlorobenzyl, hydrocarbyl substituted organometalloidradicals including trimethylsilyl, trimethylgermyl, methyldiethylsilyl,and the like, and halocarbyl-substituted organometalloid radicals,including tris(trifluoromethyl)silyl, methylbis(difluoromethyl)silyl,bromomethyldimethylgermyl and the like; and disubstituted boron radicalsincluding dimethylboron, for example; and disubstituted Group 15radicals including dimethylamine, dimethylphosphine, diphenylamine,methylphenylphosphine, as well as Group 16 radicals including methoxy,ethoxy, propoxy, phenoxy, methylsulfide and ethylsulfide. Othersubstituent groups R include, but are not limited to, olefins such asolefinically unsaturated substituents including vinyl-terminated ligandssuch as, for example, 3-butenyl, 2-propenyl, 5-hexenyl, and the like. Inone exemplary embodiment, at least two R groups (two adjacent R groupsin a particular exemplary embodiment) are joined to form a ringstructure having from 3 to 30 atoms selected from the group consistingof carbon, nitrogen, oxygen, phosphorous, silicon, germanium, aluminum,boron, and combinations thereof. Also, a substituent group R such as1-butanyl can form a bonding association to the element M.

Each leaving group, or X, in the structure (VI) above and for thestructure (VII) below is independently selected from the groupconsisting of: halogen ions, hydrides, C1 to C12 alkyls, C2 to C12alkenyls, C6 to C12 aryls, C7 to C20 alkylaryls, C1 to C12 alkoxys, C6to C16 aryloxys, C7 to C8 alkylaryloxys, C1 to C12 fluoroalkyls, C6 toC12 fluoroaryls, and C1 to C12 heteroatom-containing hydrocarbons andsubstituted derivatives thereof, in a more particular exemplaryembodiment; hydride, halogen ions, C1 to C6 alkyls, C2 to C6 alkenyls,C7 to C18 alkylaryls, C1 to C6 alkoxys, C6 to C14 aryloxys, C7 to C16alkylaryloxys, C1 to C6 alkylcarboxylates, C1 to C6 fluorinatedalkylcarboxylates, C6 to C12 arylcarboxylates, C7 to C18alkylarylcarboxylates, C1 to C6 fluoroalkyls, C2 to C6 fluoroalkenyls,and C7 to C18 fluoroalkylaryls in yet a more particular exemplaryembodiment; hydride, chloride, fluoride, methyl, phenyl, phenoxy,benzoxy, tosyl, fluoromethyls and fluorophenyls, in yet a moreparticular exemplary embodiment; C1 to C12 alkyls, C2 to C12 alkenyls,C6 to C12 aryls, C7 to C20 alkylaryls, substituted C1 to C12 alkyls,substituted C6 to C12 aryls, substituted C7 to C20 alkylaryls and C1 toC12 heteroatom-containing alkyls, C1 to C12 heteroatom-containing aryls,and C1 to C12 heteroatom-containing alkylaryls, in yet a more particularexemplary embodiment; chloride, fluoride, C1 to C6 alkyls, C2 to C6alkenyls, C7 to C18 alkylaryls, halogenated C1 to C6 alkyls, halogenatedC2 to C6 alkenyls, and halogenated C7 to C18 alkylaryls, in yet a moreparticular exemplary embodiment; chloride, methyl, ethyl, propyl,phenyl, methylphenyl, dimethylphenyl, trimethylphenyl, fluoromethyls(mono-, di- and trifluoromethyls) and fluorophenyls (mono-, di-, tri-,tetra- and pentafluorophenyls), in yet a more particular exemplaryembodiment.

Other non-limiting examples of X groups include amides, amines,phosphines, ethers, carboxylates, dienes, hydrocarbon radicals havingfrom 1 to 20 carbon atoms, fluorinated hydrocarbon radicals (e.g., —C6F5(pentafluorophenyl)), fluorinated alkylcarboxylates (e.g., CF3C(O)O—),hydrides, halogen ions and combinations thereof. Other examples of Xligands include alkyl groups such as cyclobutyl, cyclohexyl, methyl,heptyl, tolyl, trifluoromethyl, tetramethylene, pentamethylene,methylidene, methyoxy, ethyoxy, propoxy, phenoxy, bis(N-methylanilide),dimethylamide, dimethylphosphide radicals and the like. In one exemplaryembodiment, two or more X's form a part of a fused ring or ring system.In at least one specific embodiment, X can be a leaving group selectedfrom the group consisting of chloride ions, bromide ions, C1 to C10alkyls, and C2 to C12 alkenyls, carboxylates, acetylacetonates, andalkoxides.

The metallocene catalyst compound includes those of structure (VI) whereCp^(A) and Cp^(B) are bridged to each other by at least one bridginggroup, (A), such that the structure is represented by structure (VII):Cp^(A)(A)Cp^(B)MX_(n).

These bridged compounds represented by structure (VII) are known as“bridged metallocenes.” The elements Cp^(A), Cp^(B), M, X and n instructure (VII) are as defined above for structure (VI); where each Cpligand is chemically bonded to M, and (A) is chemically bonded to eachCp. The bridging group (A) can include divalent hydrocarbon groupscontaining at least one Group 13 to 16 atom, such as, but not limitedto, at least one of a carbon, oxygen, nitrogen, silicon, aluminum,boron, germanium, tin atom, and combinations thereof; where theheteroatom can also be C1 to C12 alkyl or aryl substituted to satisfyneutral valency. In at least one specific embodiment, the bridging group(A) can also include substituent groups R as defined above (forstructure (VI)) including halogen radicals and iron. In at least onespecific embodiment, the bridging group (A) can be represented by C1 toC6 alkylenes, substituted C1 to C6 alkylenes, oxygen, sulfur, R′2C═,R′2Si═, ═Si(R′)2Si(R′2)=, R′2Ge═, and R′P═, where “=” represents twochemical bonds, R′ is independently selected from the group consistingof hydride, hydrocarbyl, substituted hydrocarbyl, halocarbyl,substituted halocarbyl, hydrocarbyl-substituted organometalloid,halocarbyl-substituted organometalloid, disubstituted boron,disubstituted Group 15 atoms, substituted Group 16 atoms, and halogenradical; and where two or more R′ can be joined to form a ring or ringsystem. In at least one specific embodiment, the bridged metallocenecatalyst compound of structure (VII) includes two or more bridginggroups (A). In one or more embodiments, (A) can be a divalent bridginggroup bound to both CpA and CpB selected from the group consisting ofdivalent C1 to C20 hydrocarbyls and C1 to C20 heteroatom containinghydrocarbonyls, where the heteroatom containing hydrocarbonyls includefrom one to three heteroatoms.

The bridging group (A) can include methylene, ethylene, ethylidene,propylidene, isopropylidene, diphenylmethylene, 1,2-dimethylethylene,1,2-diphenylethylene, 1,1,2,2-tetramethylethylene, dimethylsilyl,diethylsilyl, methyl-ethylsilyl, trifluoromethylbutylsilyl,bis(trifluoromethyl)silyl, di(n-butyl)silyl, di(n-propyl)silyl,di(i-propyl)silyl, di(n-hexyl)silyl, dicyclohexylsilyl, diphenylsilyl,cyclohexylphenylsilyl, t-butylcyclohexylsilyl, di(t-butylphenyl)silyl,di(p-tolyl)silyl and the corresponding moieties where the Si atom isreplaced by a Ge or a C atom; as well as dimethylsilyl, diethylsilyl,dimethylgermyl and diethylgermyl.

The bridging group (A) can also be cyclic, having, for example, 4 to 10ring members; in a more particular exemplary embodiment, bridging group(A) can have 5 to 7 ring members. The ring members can be selected fromthe elements mentioned above, and, in a particular embodiment, can beselected from one or more of B, C, Si, Ge, N, and O. Non-limitingexamples of ring structures which can be present as, or as part of, thebridging moiety are cyclobutylidene, cyclopentylidene, cyclohexylidene,cycloheptylidene, cyclooctylidene and the corresponding rings where oneor two carbon atoms are replaced by at least one of Si, Ge, N and O. Inone or more embodiments, one or two carbon atoms can be replaced by atleast one of Si and Ge. The bonding arrangement between the ring and theCp groups can be cis-, trans-, or a combination thereof.

The cyclic bridging groups (A) can be saturated or unsaturated and/orcan carry one or more substituents and/or can be fused to one or moreother ring structures. If present, the one or more substituents can be,in at least one specific embodiment, selected from the group consistingof hydrocarbyl (e.g., alkyl, such as methyl) and halogen (e.g., F, CO.The one or more Cp groups to which the above cyclic bridging moietiescan optionally be fused can be saturated or unsaturated, and areselected from the group consisting of those having 4 to 10, moreparticularly 5, 6, or 7 ring members (selected from the group consistingof C, N, O, and S in a particular exemplary embodiment) such as, forexample, cyclopentyl, cyclohexyl and phenyl. Moreover, these ringstructures can themselves be fused such as, for example, in the case ofa naphthyl group. Moreover, these (optionally fused) ring structures cancarry one or more substituents. Illustrative, non-limiting examples ofthese substituents are hydrocarbyl (particularly alkyl) groups andhalogen atoms. The ligands Cp^(A) and Cp^(B) of structure (VI) and (VII)can be different from each other. The ligands Cp^(A) and Cp^(B) ofstructure (VI) and (VII) can be the same. The metallocene catalystcompound can include bridged mono-ligand metallocene compounds (e.g.,mono cyclopentadienyl catalyst components).

It is contemplated that the metallocene catalyst components discussedand described above include their structural or optical or enantiomericisomers (racemic mixture), and, in one exemplary embodiment, can be apure enantiomer. As used herein, a single, bridged, asymmetricallysubstituted metallocene catalyst compound having a racemic and/or mesoisomer does not, itself, constitute at least two different bridged,metallocene catalyst components.

The catalyst system can include other single site catalysts such asGroup 15-containing catalysts. The catalyst system can include one ormore second catalysts in addition to the single site catalyst compoundsuch as chromium-based catalysts, Ziegler-Natta catalysts, one or moreadditional single-site catalysts such as metallocenes or Group15-containing catalysts, bimetallic catalysts, and mixed catalysts. Thecatalyst system can also include AlCl₃, cobalt, iron, palladium, or anycombination thereof.

Group 15 Atom and Non-Metallocene Catalyst Compounds

The catalyst system can include one or more Group 15 metal-containingcatalyst compounds. As used herein, these are termed non-metallocenecatalyst compounds. The Group 15 metal-containing compound generallyincludes a Group 3 to 14 metal atom, a Group 3 to 7, or a Group 4 to 6metal atom. In many embodiments, the Group 15 metal-containing compoundincludes a Group 4 metal atom bound to at least one leaving group andalso bound to at least two Group 15 atoms, at least one of which is alsobound to a Group 15 or 16 atom through another group.

In one or more embodiments, at least one of the Group 15 atoms is alsobound to a Group 15 or 16 atom through another group which may be a C1to C20 hydrocarbon group, a heteroatom containing group, silicon,germanium, tin, lead, or phosphorus, wherein the Group 15 or 16 atom mayalso be bound to nothing or a hydrogen, a Group 14 atom containinggroup, a halogen, or a heteroatom containing group, and wherein each ofthe two Group 15 atoms are also bound to a cyclic group and canoptionally be bound to hydrogen, a halogen, a heteroatom or ahydrocarbyl group, or a heteroatom containing group.

The Group 15-containing metal compounds may be represented by a compoundof any one of structures (VIII) or (IX):

where M is a Group 3 to 12 transition metal or a Group 13 or 14 maingroup metal, a Group 4, 5, or 6 metal. In many embodiments, M is a Group4 metal, such as zirconium, titanium, or hafnium. Each X isindependently a leaving group, such as an anionic leaving group. Theleaving group may include a hydrogen, a hydrocarbyl group, a heteroatom,a halogen, or an alkyl; y is 0 or 1 (when y is 0 group L′ is absent).The term ‘n’ is the oxidation state of M. In various embodiments, n is+3, +4, or +5. In many embodiments, n is +4. The term ‘m’ represents theformal charge of the YZL or the YZL′ ligand, and is 0, −1, −2 or −3 invarious embodiments. In many embodiments, m is −2. L is a Group 15 or 16element, such as nitrogen or oxygen; L′ is a Group 15 or 16 element orGroup 14 containing group, such as carbon, silicon or germanium. Y is aGroup 15 element, such as nitrogen or phosphorus. In many embodiments, Yis nitrogen. Z is a Group 15 element, such as nitrogen or phosphorus. Inmany embodiments, Z is nitrogen. R¹ and R² are, independently, a C₁ toC₂₀ hydrocarbon group, a heteroatom containing group having up to twentycarbon atoms, silicon, germanium, tin, lead, or phosphorus. In manyembodiments, R¹ and R² are a C₂ to C₂₀ alkyl, aryl or aralkyl group,such as a linear, branched or cyclic C₂ to C₂₀ alkyl group, or a C₂ toC₆ hydrocarbon group, such as the X described with respect to structures(VI) and (VII) above. R¹ and R² may also be interconnected to eachother. R³ may be absent or may be a hydrocarbon group, a hydrogen, ahalogen, a heteroatom containing group. In many embodiments, R³ isabsent, for example, if L is an oxygen, or a hydrogen, or a linear,cyclic, or branched alkyl group having 1 to 20 carbon atoms. R⁴ and R⁵are independently an alkyl group, an aryl group, substituted aryl group,a cyclic alkyl group, a substituted cyclic alkyl group, a cyclic aralkylgroup, a substituted cyclic aralkyl group, or multiple ring system,often having up to 20 carbon atoms. In many embodiments, R⁴ and R⁵ havebetween 3 and 10 carbon atoms, or are a C₁ to C₂₀ hydrocarbon group, aC₁ to C₂₀ aryl group or a C₁ to C₂₀ aralkyl group, or a heteroatomcontaining group. R⁴ and R⁵ may be interconnected to each other. R⁶ andR⁷ are independently absent, hydrogen, an alkyl group, halogen,heteroatom, or a hydrocarbyl group, such as a linear, cyclic or branchedalkyl group having 1 to 20 carbon atoms. In many embodiments, R⁶ and R⁷are absent. R* may be absent, or may be a hydrogen, a Group 14 atomcontaining group, a halogen, or a heteroatom containing group.

By “formal charge of the YZL or YZL′ ligand,” it is meant the charge ofthe entire ligand absent the metal and the leaving groups X. By “R¹ andR² may also be interconnected” it is meant that R1 and R2 may bedirectly bound to each other or may be bound to each other through othergroups. By “R4 and R5 may also be interconnected” it is meant that R4and R5 may be directly bound to each other or may be bound to each otherthrough other groups. An alkyl group may be linear, branched alkylradicals, alkenyl radicals, alkynyl radicals, cycloalkyl radicals, arylradicals, acyl radicals, aroyl radicals, alkoxy radicals, aryloxyradicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonylradicals, aryloxycarbonyl radicals, carbamoyl radicals, alkyl- ordialkyl-carbamoyl radicals, acyloxy radicals, acylamino radicals,aroylamino radicals, straight, branched or cyclic, alkylene radicals, orcombination thereof. An aralkyl group is defined to be a substitutedaryl group.

In one or more embodiments, R4 and R5 are independently a grouprepresented by the following structure (X).

When R⁴ and R⁵ are as formula VII, R⁸ to R¹² are each independentlyhydrogen, a C₁ to C₄₀ alkyl group, a halide, a heteroatom, a heteroatomcontaining group containing up to 40 carbon atoms. In many embodiments,R⁸ to R¹² are a C₁ to C₂₀ linear or branched alkyl group, such as amethyl, ethyl, propyl, or butyl group. Any two of the R groups may forma cyclic group and/or a heterocyclic group. The cyclic groups may bearomatic. In one embodiment R⁹, R¹⁰ and R¹² are independently a methyl,ethyl, propyl, or butyl group (including all isomers). In anotherembodiment, R⁹, R¹⁰ and R¹² are methyl groups, and R⁸ and R¹¹ arehydrogen.

In one or more embodiments, R⁴ and R⁵ are both a group represented bythe following structure (XI).

When R⁴ and R⁵ follow structure (XI), M is a Group 4 metal, such aszirconium, titanium, or hafnium. In many embodiments, M is zirconium.Each of L, Y, and Z may be a nitrogen. Each of R¹ and R² may be—CH₂—CH₂—. R³ may be hydrogen, and R⁶ and R² may be absent. The Group 15metal-containing catalyst compound can be represented by structure (IV).In formula IV, Ph represents phenyl.

Catalyst Forms

The catalyst system may include a catalyst component in a slurry, whichmay have an initial catalyst compound, and an added solution catalystcomponent that is added to the slurry. The initial catalyst componentslurry may have no catalysts. In this case, two or more solutioncatalysts may be added to the slurry to cause each to be supported.

Any number of catalyst components may be used in embodiments. Forexample, the catalyst component slurry can include an activator and asupport, or a supported activator. Further, the slurry can include acatalyst compound in addition to the activator and the support. Asnoted, the catalyst compound in the slurry may be supported.

The slurry may include one or more activators and supports, and one morecatalyst compounds. For example, the slurry may include two or moreactivators (such as alumoxane and a modified alumoxane) and a catalystcompound, or the slurry may include a supported activator and more thanone catalyst compounds. In one embodiment, the slurry includes asupport, an activator, and two catalyst compounds. In another embodimentthe slurry includes a support, an activator and two different catalystcompounds, which may be added to the slurry separately or incombination.

The molar ratio of metal in the activator to metal in the pre-catalystcompound in the slurry may be 1000:1 to 0.5:1, 300:1 to 1:1, or 150:1 to1:1. The slurry can include a support material which may be any inertparticulate carrier material known in the art, including, but notlimited to, silica, fumed silica, alumina, clay, talc or other supportmaterials such as disclosed above. In one embodiment, the slurrycontains silica and an activator, such as methyl aluminoxane (“MAO”) ormodified methyl aluminoxane (“MMAO”), as discussed further below.

One or more diluents or carriers can be used to facilitate thecombination of any two or more components of the catalyst system in theslurry or in the trim catalyst solution. For example, the single sitecatalyst compound and the activator can be combined together in thepresence of toluene or another non-reactive hydrocarbon or hydrocarbonmixture to provide the catalyst mixture. In addition to toluene, othersuitable diluents can include, but are not limited to, ethylbenzene,xylene, pentane, isopentane, hexane, isohexane, heptane, octane, otherhydrocarbons, or any combination thereof. The support, either dry ormixed with toluene can then be added to the catalyst mixture or thecatalyst/activator mixture can be added to the support.

The catalyst is not limited to a slurry arrangement, as a mixed catalystsystem may be made on a support and dried. The dried catalyst system canthen be fed to the reactor through a dry feed system.

Catalyst Supports

As used herein, the terms “support” and “carrier” are usedinterchangeably and refer to any support material, including a poroussupport material, such as talc, inorganic oxides, and inorganicchlorides. The one or more single site catalyst compounds of the slurrycan be supported on the same or separate supports together with theactivator, or the activator can be used in an unsupported form, or canbe deposited on a support different from the single site catalystcompounds, or any combination thereof. This may be accomplished by anytechnique commonly used in the art. There are various other methods inthe art for supporting a single site catalyst compound. For example, thesingle site catalyst compound can contain a polymer bound ligand. Thesingle site catalyst compounds of the slurry can be spray dried. Thesupport used with the single site catalyst compound can befunctionalized, or with at least one substituent or leaving group isselected.

The support can be or include one or more inorganic oxides, for example,of Group 2, 3, 4, 5, 13, or 14 elements. The inorganic oxide caninclude, but is not limited to silica, alumina, titania, zirconia,boria, zinc oxide, magnesia, or any combination thereof. Illustrativecombinations of inorganic oxides can include, but are not limited to,alumina-silica, silica-titania, alumina-silica-titania,alumina-zirconia, alumina-titania, and the like. The support can be orinclude silica, alumina, or a combination thereof. In one embodimentdescribed herein, the support is silica.

Commercially available silica supports can include, but are not limitedto, ES757, ES70, and ES70W available from PQ Corporation. Commerciallyavailable silica-alumina supports can include, but are not limited to,SIRAL® 1, SIRAL® 5, SIRAL® 10, SIRAL® 20, SIRAL® 28M, SIRAL® 30, andSIRAL® 40, available from SASOL®. Generally, catalyst supportscomprising silica gels with activators, such as methylaluminoxanes(MAOs), are used in the trim systems described, since these supports mayfunction better for co-supporting solution carried catalysts. Suitablesupports may also be selected from the Cab-o-Sil® materials availablefrom Cabot Corporation and silica materials available from the Gracedivision of W.R. Grace & Company.

Catalyst Activators

As used herein, the term “activator” may refer to any compound orcombination of compounds, supported, or unsupported, which can activatea single site catalyst compound or component, such as by creating acationic species of the catalyst component. For example, this caninclude the abstraction of at least one leaving group (the “X” group inthe single site catalyst compounds described herein) from the metalcenter of the single site catalyst compound/component. The activator mayalso be referred to as a “co-catalyst”.

For example, the activator can include a Lewis acid or anon-coordinating ionic activator or ionizing activator, or any othercompound including Lewis bases, aluminum alkyls, and/orconventional-type co-catalysts. In addition to methylaluminoxane (“MAO”)and modified methylaluminoxane (“MMAO”) mentioned above, illustrativeactivators can include, but are not limited to, aluminoxane or modifiedaluminoxane, and/or ionizing compounds, neutral or ionic, such as tri(n-butyl)ammonium tetrakis(pentafluorophenyl)boron, atrisperfluorophenyl boron metalloid precursor, a trisperfluoronaphthylboron metalloid precursor, or any combinations thereof.

It is recognized that these activators may or may not bind directly tothe support surface or may be modified to allow them to be bound to asupport surface while still maintaining their compatibility with thepolymerization system. Such tethering agents may be derived from groupsthat are reactive with surface hydroxyl species. Non-limiting examplesof reactive functional groups that can be used to create tethers includealuminum halides, aluminum hydrides, aluminum alkyls, aluminum aryls,aluminum alkoxides, electrophilic silicon reagents, alkoxy silanes,amino silanes, boranes.

Aluminoxanes can be described as oligomeric aluminum compounds having—Al(R)—O— subunits, where R is an alkyl group. Examples of aluminoxanesinclude, but are not limited to, methylaluminoxane (“MAO”), modifiedmethylaluminoxane (“MMAO”), ethylaluminoxane, isobutylaluminoxane, or acombination thereof. Aluminoxanes can be produced by the hydrolysis ofthe respective trialkylaluminum compound. MMAO can be produced by thehydrolysis of trimethylaluminum and a higher trialkylaluminum, such astriisobutylaluminum. MMAOs are generally more soluble in aliphaticsolvents and more stable during storage. There are a variety of methodsfor preparing aluminoxane and modified aluminoxanes.

As noted above, one or more organo-aluminum compounds such as one ormore alkylaluminum compounds can be used in conjunction with thealuminoxanes. For example, alkylaluminum species that may be used arediethylaluminum ethoxide, diethylaluminum chloride, and/ordiisobutylaluminum hydride. Examples of trialkylaluminum compoundsinclude, but are not limited to, trimethylaluminum, triethylaluminum(“TEAL”), triisobutylaluminum (“TiBAl”), tri-n-hexylaluminum,tri-n-octylaluminum, tripropylaluminum, tributylaluminum, and the like.

Catalyst Component Solutions

The catalyst component solution may include only a catalyst compound,such as a metallocene, or may include an activator in addition to thecatalyst compound. The catalyst solution used in the trim process can beprepared by dissolving the catalyst compound and optional activators ina liquid solvent. The liquid solvent may be an alkane, such as a C5 toC30 alkane, or a C5 to C10 alkane. Cyclic alkanes such as cyclohexaneand aromatic compounds such as toluene may also be used. In addition,mineral oil may be used as a solvent. The solution employed should beliquid under the conditions of polymerization and relatively inert. Inone embodiment, the liquid utilized in the catalyst compound solution isdifferent from the diluent used in the catalyst component slurry. Inanother embodiment, the liquid utilized in the catalyst compoundsolution is the same as the diluent used in the catalyst componentsolution.

If the catalyst solution includes both activator and catalyst compound,the ratio of metal in the activator to metal in the catalyst compound inthe solution may be 1000:1 to 0.5:1, 300:1 to 1:1, or 150:1 to 1:1. Invarious embodiments, the activator and catalyst compound are present inthe solution at up to about 90 wt. %, at up to about 50 wt. %, at up toabout 20 wt. %, preferably at up to about 10 wt. %, at up to about 5 wt.%, at less than 1 wt. %, or between 100 ppm and 1 wt. %, based upon theweight of the solvent and the activator or catalyst compound.

The catalyst component solution can include any one of the solublecatalyst compounds described in the catalyst section herein. As thecatalyst is dissolved in the solution, a higher solubility is desirable.Accordingly, the catalyst compound in the catalyst component solutionmay often include a metallocene, which may have higher solubility thanother catalysts.

In the polymerization process described below, any of the abovedescribed catalyst component containing solutions may be combined withany of the catalyst component containing slurry/slurries describedabove. In addition, more than one catalyst component solution may beutilized.

Continuity Additive/Static Control Agent

In gas-phase polyethylene production processes, it may be desirable touse one or more static control agents to aid in regulating static levelsin the reactor. As used herein, a static control agent is a chemicalcomposition which, when introduced into a fluidized bed reactor, mayinfluence or drive the static charge (negatively, positively, or tozero) in the fluidized bed. The specific static control agent used maydepend upon the nature of the static charge, and the choice of staticcontrol agent may vary dependent upon the polymer being produced and thesingle site catalyst compounds being used.

Control agents such as aluminum stearate may be employed. The staticcontrol agent used may be selected for its ability to receive the staticcharge in the fluidized bed without adversely affecting productivity.Other suitable static control agents may also include aluminumdistearate, ethoxylated amines, and anti-static compositions such asthose provided by Innospec Inc. under the trade name OCTASTAT. Forexample, OCTASTAT 2000 is a mixture of a polysulfone copolymer, apolymeric polyamine, and oil-soluble sulfonic acid.

The aforementioned control agents and other control agents or antistaticagents may be employed either alone or in combination as a controlagent. For example, the carboxylate metal salt may be combined with anamine containing control agent (e.g., a carboxylate metal salt with anyfamily member belonging to the KEMAMINE® (available from CromptonCorporation) or ATMER® (available from ICI Americas Inc.) family ofproducts).

Other useful continuity additives include ethyleneimine additives usefulin embodiments disclosed herein may include polyethyleneimines havingthe following general formula:—(CH₂—CH₂—NH)_(n)—,in which n may be from about 10 to about 10,000. The polyethyleneiminesmay be linear, branched, or hyperbranched (e.g., forming dendritic orarborescent polymer structures). They can be a homopolymer or copolymerof ethyleneimine or mixtures thereof (referred to aspolyethyleneimine(s) hereafter). Although linear polymers represented bythe chemical formula —[CH2-CH2-NH]— may be used as thepolyethyleneimine, materials having primary, secondary, and tertiarybranches can also be used. Commercial polyethyleneimine can be acompound having branches of the ethyleneimine polymer. Suitablepolyethyleneimines are commercially available from BASF Corporationunder the trade name Lupasol. These compounds can be prepared as a widerange of molecular weights and product activities. Examples ofcommercial polyethyleneimines sold by BASF suitable for use in thepresent invention include, but are not limited to, Lupasol FG andLupasol WF.

Another useful continuity additive can include a mixture of aluminumdistearate and an ethoxylated amine-type compound, e.g., IRGASTATAS-990, available from Huntsman (formerly Ciba Specialty Chemicals). Themixture of aluminum distearate and ethoxylated amine type compound canbe slurried in mineral oil e.g., Hydrobrite 380. For example, themixture of aluminum distearate and an ethoxylated amine type compoundcan be slurried in mineral oil to have total slurry concentration ofranging from about 5 wt. % to about 50 wt. % or about 10 wt. % to about40 wt. %, or about 15 wt. % to about 30 wt. %. Other static controlagents and additives are contemplated.

The continuity additive(s) or static control agent(s) may be added tothe reactor in an amount ranging from 0.05 to 200 ppm, based on theweight of all feeds to the reactor, excluding recycle. In someembodiments, the continuity additive may be added in an amount rangingfrom 2 to 100 ppm, or in an amount ranging from 4 to 50 ppm.

Gas Phase Polymerization Reactor

FIG. 2 is a schematic of a gas-phase reactor system 200, showing theaddition of at least two catalysts, at least one of which is added as atrim catalyst. The catalyst component slurry, preferably a mineral oilslurry including at least one support and at least one activator, atleast one supported activator, and optional catalyst compounds may beplaced in a vessel or catalyst pot (cat pot) 202. In one embodiment, thecat pot 202 is an agitated holding tank designed to keep the solidsconcentration homogenous. A catalyst component solution, prepared bymixing a solvent and at least one catalyst compound and/or activator, isplaced in another vessel, which can be termed a trim pot 204. Thecatalyst component slurry can then be combined in-line with the catalystcomponent solution to form a final catalyst composition. A nucleatingagent 206, such as silica, alumina, fumed silica or any otherparticulate matter may be added to the slurry and/or the solutionin-line or in the vessels 202 or 204. Similarly, additional activatorsor catalyst compounds may be added in-line. For example, a secondcatalyst slurry that includes a different catalyst may be introducedfrom a second cat pot. The two catalyst slurries may be used as thecatalyst system with or without the addition of a solution catalyst fromthe trim pot.

The catalyst component slurry and solution can be mixed in-line. Forexample, the solution and slurry may be mixed by utilizing a staticmixer 208 or an agitating vessel (not shown). The mixing of the catalystcomponent slurry and the catalyst component solution should be longenough to allow the catalyst compound in the catalyst component solutionto disperse in the catalyst component slurry such that the catalystcomponent, originally in the solution, migrates to the supportedactivator originally present in the slurry. The combination forms auniform dispersion of catalyst compounds on the supported activatorforming the catalyst composition. The length of time that the slurry andthe solution are contacted is typically up to about 220 minutes, such asabout 1 to about 60 minutes, about 5 to about 40 minutes, or about 10 toabout 30 minutes.

When combining the catalysts, the activator and the optional support oradditional co-catalysts, in the hydrocarbon solvents immediately priorto a polymerization reactor it is desirable that the combination yield anew polymerization catalyst in less than 1 h, less than 30 min, or lessthan 15 min. Shorter times are more effective, as the new catalyst isready before being introduces into the reactor, providing the potentialfor faster flow rates.

In another embodiment, an aluminum alkyl, an ethoxylated aluminum alkyl,an aluminoxane, an anti-static agent or a borate activator, such as a C1to C15 alkyl aluminum (for example tri-isobutyl aluminum, trimethylaluminum or the like), a C1 to C15 ethoxylated alkyl aluminum or methylaluminoxane, ethyl aluminoxane, isobutylaluminoxane, modifiedaluminoxane or the like are added to the mixture of the slurry and thesolution in line. The alkyls, antistatic agents, borate activatorsand/or aluminoxanes may be added from an alkyl vessel 210 directly tothe combination of the solution and the slurry, or may be added via anadditional alkane (such as isopentane, hexane, heptane, and or octane)carrier stream, for example, from a hydrocarbon vessel 212. Theadditional alkyls, antistatic agents, borate activators and/oraluminoxanes may be present at up to about 500 ppm, at about 1 to about300 ppm, at 10 to about 300 ppm, or at about 10 to about 100 ppm.Carrier streams that may be used include isopentane and or hexane, amongothers. The carrier may be added to the mixture of the slurry and thesolution, typically at a rate of about 0.5 to about 60 lbs/hr (27kg/hr). Likewise a carrier gas 214, such as nitrogen, argon, ethane,propane, and the like, may be added in-line to the mixture of the slurryand the solution. Typically the carrier gas may be added at the rate ofabout 1 to about 100 lb/hr (0.4 to 45 kg/hr), or about 1 to about 50lb/hr (5 to 23 kg/hr), or about 1 to about 25 lb/hr (0.4 to 11 kg/hr).

In another embodiment, a liquid carrier stream is introduced into thecombination of the solution and slurry that is moving in a downwarddirection. The mixture of the solution, the slurry and the liquidcarrier stream may pass through a mixer or length of tube for mixingbefore being contacted with a gaseous carrier stream.

Similarly, a comonomer 216, such as hexene, another alpha-olefin, ordiolefin, may be added in-line to the mixture of the slurry and thesolution. The slurry/solution mixture is then passed through aninjection tube 220 to a reactor 222. In some embodiments, the injectiontube may aerosolize the slurry/solution mixture. Any number of tubingsizes and configurations may be used to aerosolize and/or inject theslurry/solution mixture.

In one embodiment, a gas stream 226, such as cycle gas, or re-cycle gas224, monomer, nitrogen, or other materials is introduced into a supporttube 228 that surrounds the injection tube 220. To assist in properformation of particles in the reactor 222, a nucleating agent 218, suchas fumed silica, can be added directly into the reactor 222.

When a metallocene catalyst or other similar catalyst is used in the gasphase reactor, oxygen or fluorobenzene can be added to the reactor 222directly or to the gas stream 226 to control the polymerization rate.Thus, when a metallocene catalyst (which is sensitive to oxygen orfluorobenzene) is used in combination with another catalyst (that is notsensitive to oxygen) in a gas phase reactor, oxygen can be used tomodify the metallocene polymerization rate relative to thepolymerization rate of the other catalyst. An example of such a catalystcombination is bis(n-propyl cyclopentadienyl)zirconium dichloride and[(2,4,6-Me3C6H2)NCH2 CH2]2NHZrBn2, where Me is methyl, orbis(indenyl)zirconium dichloride and [(2,4,6-Me3C6H2)NCH2CH2]2NHHfBn2,where Me is methyl. For example, if the oxygen concentration in thenitrogen feed is altered from 0.1 ppm to 0.5 ppm, significantly lesspolymer from the bisindenyl ZrCl2 will be produced and the relativeamount of polymer produced from the [(2,4,6-Me3C6H2)NCH2CH2]2NHHfBn2 isincreased. The addition of water or carbon dioxide to gas phasepolymerization reactors, for example, may be applicable for similarpurposes. In one embodiment, the contact temperature of the slurry andthe solution is in the range of from 0° C. to about 80° C., from about0° C. to about 60° C., from about 10° C., to about 50° C., and fromabout 20° C. to about 40° C.

The example above is not limiting, as additional solutions and slurriesmay be included. For example, a slurry can be combined with two or moresolutions having the same or different catalyst compounds and oractivators. Likewise, the solution may be combined with two or moreslurries each having the same or different supports, and the same ordifferent catalyst compounds and or activators. Similarly, two or moreslurries combined with two or more solutions, preferably in-line, wherethe slurries each comprise the same or different supports and maycomprise the same or different catalyst compounds and or activators andthe solutions comprise the same or different catalyst compounds and oractivators. For example, the slurry may contain a supported activatorand two different catalyst compounds, and two solutions, each containingone of the catalysts in the slurry, are each independently combined,in-line, with the slurry.

Use of Catalyst Composition to Control Product Properties

The properties of the product polymer may be controlled by adjusting thetiming, temperature, concentrations, and sequence of the mixing of thesolution, the slurry and any optional added materials (nucleatingagents, catalyst compounds, activators, etc) described above. The MWD,melt index, relative amount of polymer produced by each catalyst, andother properties of the polymer produced may also be changed bymanipulating process parameters. Any number of process parameters may beadjusted, including manipulating hydrogen concentration in thepolymerization system, changing the amount of the first catalyst in thepolymerization system, changing the amount of the second catalyst in thepolymerization system. Other process parameters that can be adjustedinclude changing the relative ratio of the catalyst in thepolymerization process (and optionally adjusting their individual feedrates to maintain a steady or constant polymer production rate). Theconcentrations of reactants in the reactor 222 can be adjusted bychanging the amount of liquid or gas that is withdrawn or purged fromthe process, changing the amount and/or composition of a recoveredliquid and/or recovered gas returned to the polymerization process,wherein the recovered liquid or recovered gas can be recovered frompolymer discharged from the polymerization process. Furtherconcentration parameters that can be adjusted include changing thepolymerization temperature, changing the ethylene partial pressure inthe polymerization process, changing the ethylene to comonomer ratio inthe polymerization process, changing the activator to transition metalratio in the activation sequence. Time dependent parameters may beadjusted, such as changing the relative feed rates of the slurry orsolution, changing the mixing time, the temperature and or degree ofmixing of the slurry and the solution in-line, adding different types ofactivator compounds to the polymerization process, and adding oxygen orfluorobenzene or other catalyst poison to the polymerization process.Any combinations of these adjustments may be used to control theproperties of the final polymer product.

In one embodiment, the MWD of the polymer product is measured at regularintervals and one of the above process parameters, such as temperature,catalyst compound feed rate, the ratios of the two or more catalysts toeach other, the ratio of comonomer to monomer, the monomer partialpressure, and or hydrogen concentration, is altered to bring thecomposition to the desired level, if necessary. The MWD may be measuredby size exclusion chromatography (SEC), e.g., gel permeationchromatography (GPC), among other techniques.

In one embodiment, a polymer product property is measured in-line and inresponse the ratio of the catalysts being combined is altered. In oneembodiment, the molar ratio of the catalyst compound in the catalystcomponent slurry to the catalyst compound in the catalyst componentsolution, after the slurry and solution have been mixed to form thefinal catalyst composition, is 500:1 to 1:500, or 100:1 to 1:100, or50:1 to 1:50 or 40:1 to 1:10. In another embodiment, the molar ratio ofa Group 15 catalyst compound in the slurry to a ligand metallocenecatalyst compound in the solution, after the slurry and solution havebeen mixed to form the catalyst composition, is 500:1, 100:1, 50:1,10:1, or 5:1. The product property measured can include the dynamicshear viscosity, flow index, melt index, density, MWD, comonomercontent, and combinations thereof. In another embodiment, when the ratioof the catalyst compounds is altered, the introduction rate of thecatalyst composition to the reactor, or other process parameters, isaltered to maintain a desired production rate.

Polymerization Process

The catalyst system can be used to polymerize one or more olefins toprovide one or more polymer products therefrom. Any suitablepolymerization process can be used, including, but not limited to, highpressure, solution, slurry, and/or gas phase polymerization processes.In embodiments that use other techniques besides gas phasepolymerization, modifications to a catalyst addition system that aresimilar to those discussed with respect to FIG. 2 can be used. Forexample, a trim system may be used to feed catalyst to a loop slurryreactor for polyethylene copolymer production.

The terms “polyethylene” and “polyethylene copolymer” refer to a polymerhaving at least 50 wt. % ethylene-derived units. In various embodiments,the polyethylene can have at least 70 wt. % ethylene-derived units, atleast 80 wt. % ethylene-derived units, at least 90 wt. %ethylene-derived units, or at least 95 wt. % ethylene-derived units. Thepolyethylene polymers described herein are generally copolymer, but mayalso include terpolymers, having one or more other monomeric units. Asdescribed herein, a polyethylene can include, for example, at least oneor more other olefins or comonomers. Suitable comonomers can contain 3to 16 carbon atoms, from 3 to 12 carbon atoms, from 4 to 10 carbonatoms, and from 4 to 8 carbon atoms. Examples of comonomers include, butare not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene,1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene, andthe like. Additionally, small amounts of diene monomers, such as1,7-octadiene may be added to the polymerization to adjust polymerproperties.

Referring again to FIG. 2, the fluidized bed reactor 222 can include areaction zone 232 and a velocity reduction zone 234. The reaction zone232 can include a bed 236 that includes growing polymer particles,formed polymer particles and a minor amount of catalyst particlesfluidized by the continuous flow of the gaseous monomer and diluent toremove heat of polymerization through the reaction zone. Optionally,some of the re-circulated gases 224 can be cooled and compressed to formliquids that increase the heat removal capacity of the circulating gasstream when readmitted to the reaction zone. A suitable rate of gas flowcan be readily determined by experimentation. Make-up of gaseous monomerto the circulating gas stream can be at a rate equal to the rate atwhich particulate polymer product and monomer associated therewith iswithdrawn from the reactor and the composition of the gas passingthrough the reactor can be adjusted to maintain an essentially steadystate gaseous composition within the reaction zone. The gas leaving thereaction zone 232 can be passed to the velocity reduction zone 234 whereentrained particles are removed, for example, by slowing and fallingback to the reaction zone 232. If desired, finer entrained particles anddust can be removed in a separation system 238, such as a cyclone and/orfines filter. The gas 224 can be passed through a heat exchanger 240where at least a portion of the heat of polymerization can be removed.The gas can then be compressed in a compressor 242 and returned to thereaction zone 232.

The reactor temperature of the fluid bed process can be greater thanabout 30° C., about 40° C., about 50° C., about 90° C., about 100° C.,about 110° C., about 120° C., about 150° C., or higher. In general, thereactor temperature is operated at the highest feasible temperaturetaking into account the sintering temperature of the polymer productwithin the reactor. Thus, the upper temperature limit in one embodimentis the melting temperature of the polyethylene copolymer produced in thereactor. However, higher temperatures may result in narrower MWDs, whichcan be improved by the addition of structure (IV), or otherco-catalysts, as described herein.

Hydrogen gas can be used in olefin polymerization to control the finalproperties of the polyolefin. Using certain catalyst systems, increasingconcentrations (partial pressures) of hydrogen can increase the flowindex (FI), or melt index (MI) of the polyethylene copolymer generated.The flow index can thus be influenced by the hydrogen concentration. Theamount of hydrogen in the polymerization can be expressed as a moleratio relative to the total polymerizable monomer, for example,ethylene, or a blend of ethylene and hexene or propylene.

The amount of hydrogen used in the polymerization process can be anamount necessary to achieve the desired flow index of the finalpolyolefin polymer. For example, the mole ratio of hydrogen to totalmonomer (H2:monomer) can be greater than about 0.0001, greater thanabout 0.0005, or greater than about 0.001. Further, the mole ratio ofhydrogen to total monomer (H2:monomer) can be less than about 10, lessthan about 5, less than about 3, and less than about 0.10. A desirablerange for the mole ratio of hydrogen to monomer can include anycombination of any upper mole ratio limit with any lower mole ratiolimit described herein. Expressed another way, the amount of hydrogen inthe reactor at any time can range to up to about 5,000 ppm, up to about4,000 ppm in another embodiment, up to about 3,000 ppm, or between about50 ppm and 5,000 ppm, or between about 50 ppm and 2,000 ppm in anotherembodiment. The amount of hydrogen in the reactor can range from a lowof about 1 ppm, about 50 ppm, or about 100 ppm to a high of about 400ppm, about 800 ppm, about 1,000 ppm, about 1,500 ppm, or about 2,000ppm, based on weight. Further, the ratio of hydrogen to total monomer(H2:monomer) can be about 0.00001:1 to about 2:1, about 0.005:1 to about1.5:1, or about 0.0001:1 to about 1:1. The one or more reactor pressuresin a gas phase process (either single stage or two or more stages) canvary from 690 kPa (100 psig) to 3,448 kPa (500 psig), in the range from1,379 kPa (200 psig) to 2,759 kPa (400 psig), or in the range from 1,724kPa (250 psig) to 2,414 kPa (350 psig).

The gas phase reactor can be capable of producing from about 10 kg ofpolymer per hour (25 lbs/hr) to about 90,900 kg/hr (200,000 lbs/hr), orgreater, and greater than about 455 kg/hr (1,000 lbs/hr), greater thanabout 4,540 kg/hr (10,000 lbs/hr), greater than about 11,300 kg/hr(25,000 lbs/hr), greater than about 15,900 kg/hr (35,000 lbs/hr), andgreater than about 22,700 kg/hr (50,000 lbs/hr), and from about 29,000kg/hr (65,000 lbs/hr) to about 45,500 kg/hr (100,000 lbs/hr).

As noted, a slurry polymerization process can also be used inembodiments. A slurry polymerization process generally uses pressures inthe range of from about 101 kPa (1 atmosphere) to about 5,070 kPa (50atmospheres) or greater, and temperatures in the range of from about 0°C. to about 120° C., and more particularly from about 30° C. to about100° C. In a slurry polymerization, a suspension of solid, particulatepolymer can be formed in a liquid polymerization diluent medium to whichethylene, comonomers, and hydrogen along with catalyst can be added. Thesuspension including diluent can be intermittently or continuouslyremoved from the reactor where the volatile components are separatedfrom the polymer and recycled, optionally after a distillation, to thereactor. The liquid diluent employed in the polymerization medium can bean alkane having from 3 to 7 carbon atoms, such as, for example, abranched alkane. The medium employed should be liquid under theconditions of polymerization and relatively inert. When a propane mediumis used the process should be operated above the reaction diluentcritical temperature and pressure. In one embodiment, a hexane,isopentane, or isobutane medium can be employed. The slurry can becirculated in a continuous loop system.

The product polyethylene can have a melt flow ratio (MFR) or melt indexratio (MIR), 121/12, ranging from about 10 to less than about 300, or,in many embodiments, from about 25 to about 80. Flow index (FI, HLMI, or121) can be measured in accordance with ASTM D1238 (190° C., 21.6 kg).Melt index (MI, 12) can be measured in accordance with ASTM D1238 (at190° C., 2.16 kg weight).

Density can be determined in accordance with ASTM D-792. Density isexpressed as grams per cubic centimeter (g/cm3) unless otherwise noted.The polyethylene can have a density ranging from a low of about 0.89g/cm3, about 0.90 g/cm3, or about 0.91 g/cm3 to a high of about 0.95g/cm3, about 0.96 g/cm3, or about 0.97 g/cm3. The polyethylene can havea bulk density, measured in accordance with ASTM D1895 method B, of fromabout 0.25 g/cm3 to about 0.5 g/cm3. For example, the bulk density ofthe polyethylene can range from a low of about 0.30 g/cm3, about 0.32g/cm3, or about 0.33 g/cm3 to a high of about 0.40 g/cm3, about 0.44g/cm3, or about 0.48 g/cm3.

Gel count was determined herein using an optical control system of modelME-20/2800 extruder, a CR9 chill roll and winder unit, and FSA-100 filmanalyzer, available from Optical Control Systems (OCS) GmbH of Germany.The system consisted of a ¾ inch screw and 6 inch fixed lip. The screwspeed was 50 rpm, with a temperature profile of 190, 220, 215, 215, and215° C., a chill roll temperature of 30° C., and a take off speed ofabout 3.0 m/min to produce a film of 50 μm.

The polyethylene can be suitable for such articles as films, fibers,nonwoven and/or woven fabrics, extruded articles, and/or moldedarticles. Examples of films include blown or cast films formed in singlelayer extrusion, coextrusion, or lamination useful as shrink film, clingfilm, stretch film, sealing films, oriented films, snack packaging,heavy duty bags, grocery sacks, baked and frozen food packaging, medicalpackaging, industrial liners, membranes, etc. in food-contact andnon-food contact applications, agricultural films and sheets. Examplesof fibers include melt spinning, solution spinning and melt blown fiberoperations for use in woven or non-woven form to make filters, diaperfabrics, hygiene products, medical garments, geotextiles, etc. Examplesof extruded articles include tubing, medical tubing, wire and cablecoatings, pipe, geomembranes, and pond liners. Examples of moldedarticles include single and multi-layered constructions by injectionmolding or rotation molding or blow molding processes in the form ofbottles, tanks, large hollow articles, rigid food containers and toys,etc.

EXAMPLES

A gas phase fluidized bed reactor of 0.35 meters internal diameter and2.3 meters in bed height was utilized for all of the polymerizations.The fluidized bed was made up of polymer granules and gaseous feedstreams of ethylene and hydrogen together with liquid 1-hexene comonomerwere introduced below the reactor bed into the recycle gas line. Theindividual flow rates of ethylene, hydrogen and 1-hexene were controlledto maintain fixed composition targets. The ethylene concentration wascontrolled to maintain a constant ethylene partial pressure. Thehydrogen was controlled to maintain constant hydrogen to ethylene moleratio. The concentrations of all the gases were measured by an on-linegas chromatograph to ensure relatively constant composition in therecycle gas stream. The reacting bed of growing polymer particles wasmaintained in a fluidized state by the continuous flow of the make-upfeed and recycle gas through the reaction zone. A superficial gasvelocity of 0.6-0.9 meters/sec was used to achieve this. The fluidizedbed was maintained at a constant height by withdrawing a portion of thebed at a rate equal to the rate of formation of particulate product. Thepolymer production rate was in the range of 15-25 kg/hour. The productwas removed semi-continuously via a series of valves into a fixed volumechamber. This product was purged to remove entrained hydrocarbons andtreated with a small stream of humidified nitrogen to deactivate anytrace quantities of residual catalyst and cocatalyst.

The solid catalyst was dispersed in degassed and dried mineral oil as anominal 18 wt % slurry and contacted with the trim catalyst solution fora few seconds to minutes before being injected directly into thefluidized bed using purified nitrogen and isopentane as carriers in amanner that produces an effervescence of nitrogen in the liquid andspray to aid in dispersing the catalyst. The trim catalyst was providedinitially as a solution, and substantially diluted with isopentane to aconcentration of about 0.02 wt % or 0.04 wt % before being mixed in-linewith the slurry catalyst component in a continuous manner prior toinjection to the reactor. The relative feeds of the slurry catalyst andthe trim catalyst were controlled to achieve an aim target feed ratio oftheir active polymerization metals, and the feeds adjusted accordinglyfor overall polymer production rate and the relative amounts of polymerproduced by each catalyst based somewhat on polymer flow index MFR anddensity, while also manipulating reaction temperature and the gascompositions in the reactor. The reacting bed of growing polymerparticles was maintained in a fluidized state by continually flowing themakeup feed and recycle gas through the reaction zone at a superficialgas velocity in about the range of 2.0 to 2.2 ft/sec (0.61 to 0.67m/sec). The reactor was operated at a total pressure of about 350 psig(2413 kPa gauge). To maintain a constant fluidized bed temperature inthe reactor, the temperature of the recycle gas was continuouslyadjusted up or down by passing the recirculating gas through the tubesof a shell-and-tube heat exchanger with cooling water on the shell-sideto accommodate any changes in the rate of heat generation due to thepolymerization.

A slurry mixture of continuity additive in degassed and dried mineraloil (1:1 Aluminum stearate:N-nonyldiethanolamine at 20 wt %concentration) was fed into the reactor using a mixture of isopentaneand nitrogen.

Catalyst Preparation

All procedures were performed under nitrogen, with the exclusion of airand moisture. The combined Hf and Zr loading for all of the cosupportedmixed metallocene catalysts was about 30 μmol (Zr+Hf)/g of catalyst, andthe aluminum loading was about 4.5 mmol Al/g of catalyst. For thesecosupported mixed metallocene catalysts, the HfP/EtInd ratios used forthe catalyst preparation include 85:15, 60:40, and 50:50, on a molefraction basis, as shown below. The methylaluminoxane (MAO, Albemarle 10wt %) and the metallocenes were added to a reactor first and mixed forhalf an hour at room temperature. Silica (ES757, PQ Corp. calcined at875° C.) was then added directly into the MAO/metallocenes solution andmixed for an additional one hour at room temperature. The catalysts werethen dried under vacuum until the internal temperature was lined out at˜70° C. for 2.5 hours. The single component catalyst used in Example 1was prepared in a manner similar to that described above for the mixedmetallocene catalysts. The Hf loading for this catalyst was about 0.045mmol Hf/g of catalyst and the aluminum loading for this catalyst wasabout 4.5 mmol Al/g of catalyst. In each case, a catalyst slurry wasmade by adding the dry solid catalyst to Hydrobrite 380 mineral oil toform an 18 wt % slurry.

For preparation of the trim solution, the appropriate metallocene wasdissolved in dry, degassed isopentane. The trim solution concentrationof metallocene was 0.02 wt % for Examples 1, 2 and 4. The trim solutionconcentration of metallocene was 0.04 wt % for Example 5.

In Example 1, the catalyst system comprised a supported single componentHfP catalyst with EtInd added as trim.

In Example 2, the catalyst system comprised cosupported HfP and EthIndcatalysts, with an initial co-deposit on a mol fraction basis of 0.85HfP and 0.15 EthInd. Additional EthInd slurry was added as catalysttrim.

In Example 3, the catalyst system comprised cosupported HfP and EthIndcatalysts, with an initial co-deposit on a mol fraction basis was 0.60HfP and 0.40 EthInd. There was no trim catalyst.

In Example 4, the catalyst system comprised cosupported HfP and EthIndcatalysts, with an initial co-deposit on a mol fraction basis of 0.60EthInd and 0.40 HfP. Additional HfP slurry was added as catalyst trim.

In Example 5, the catalyst system comprised cosupported HfP and EthIndcatalysts, with an initial co-deposit on a mol fraction basis of 0.50EthInd and 0.50 HfP. Additional HfP slurry was added as catalyst trim.

Table 1 below summarizes polymerization reaction data for each ofExamples 1-5.

TABLE 1 Polymerization Reaction Data for Examples 1-5 Example 1 2 3 4 5C2 partial pressure, psia 207.6 220.1 220.0 220.0 219.9 C6/C2 molarratio 0.0193 0.0215 0.0279 0.0238 0.0270 H2/C2 ratio, ppmv/mole % 8.147.96 7.01 7.00 6.50 Reactor temp, ° C. 80 80 80 80 80 Continuityadditive, ppmw 27.30 27.30 31.19 30.86 28.94 Hf/Zr molar feed ratio 2.721.82 1.45 2.86 7.27 Residence time, hours 2.53 2.62 3.27 2.79 2.78Slurry catalyst flow rate, mL/hour 13.3 15.3 17.5 17.6 16.0 Trim Flow,g/hour 0.01414 0.00875 0 0.01995 0.11653

Table 2 below summarizes catalyst loading data for the catalysts used ineach of Examples 1-5. The catalyst loading is provided in μmol/g of thesolid dry catalyst.

TABLE 2 Catalyst Loading for Examples 1-5 Example 1 2 3 4 5 Catalyst HfLoading, μmol/g 43.7 24.8 17 17 15.7 Catalyst Zr Loading μmol/g 0 4.911.7 11.7 16.8 Initial Hf/Zr ratio (mol/mol) NA 5 1.4 1.4 0.9 FinalHf/Zr ratio (mol/mol) 2.7 1.8 1.4 2.9 7.3

Table 3 below provides polymer characteristics for the polymers producedin Examples 1-5, as well as gel data measured as described above for theextruded polymers. This gel data is 1^(st) pass data for samplesextruded on two different extruders: a Werner & Pfleiderer 57 mm TwinScrew Extruder (“WP-57”), and a Werner & Pfleiderer 30 mm Twin ScrewExtruder (“WP-30”). The WP-57 is a co-rotating twin screw extruder, withan L/D ratio of 24:1 and an underwater pelletizer. The WP-30 is aco-rotating twin screw extruder with an L/D ratio of 29:1 and anunderwater pelletizer.

TABLE 3 Polymer Characteristics and Gel Data for Examples 1-5 Example 12 3 4 5 HfP CD 85:15 CD 60:40 CD 60:40 CD 50:50 LMW-Trim LMW-Trim NoTrim HMW-Trim HMW-Trim Resin Characteristics Density (g/cm3) 0.920 0.9210.921 0.922 0.921 MI (dg/min) 0.8 0.9 1.1 1.1 1.0 MFR (I-21/I-2) 50 4960 49 58 OCS (gels per ppm in extruded resin) TDA @ 1st Pass on WP-5711,430 4,626 221 100 68 TDA @ 1st Pass on WP-30 3,492 263 38 33 16

The presence of gels in the polyethylene was significantly lower inExamples 4 and 5 versus Examples 1-3. FIG. 3 is a bar chart 300depicting the 1st-pass gel data shown in Table 3. The vertical axis 302is gels part per million (ppm) of the polyethylene, as shown in Table 3.The horizontal axis 304 is the Example numbers. The first bar in eachExample is for the 1st pass on a Werner & Pfleiderer 57 mm Twin ScrewExtruder (“WP-57”). The second bar in each Example is for the 1st passon a Werner & Pfleiderer (“WP-30”) 30 mm Twin Screw Extruder. The firstbar in Example 1 is labeled with the reference numeral 306. The secondbar in Example 1 is labeled with the reference numeral 308. As can beseen from Table 3 and FIG. 3, a significant reduction in gels isrealized in embodiments of the present techniques.

All numerical values are “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art. Further, variousterms have been defined above. To the extent a term used in a claim isnot defined above, it should be given the broadest definition persons inthe pertinent art have given that term as reflected in at least oneprinted publication or issued patent. All patents, test procedures, andother documents cited in this application are fully incorporated byreference to the extent such disclosure is not inconsistent with thisapplication and for all jurisdictions in which such incorporation ispermitted.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention can be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A method of polymerizing olefins, comprising:contacting ethylene and at least one comonomer with a catalyst system toproduce a polyolefin polymer that is multimodal, the catalyst systemcomprising a first catalyst that promotes polymerization of the ethyleneinto a low molecular weight (LMW) portion of the polyolefin polymer, anda second catalyst that promotes polymerization of the ethylene into ahigh molecular weight (HMW) portion of the polyolefin polymer; whereinthe first catalyst and at least a portion of the second catalyst areco-supported to form a commonly-supported catalyst system; and whereinat least a portion of the second catalyst is added as a catalyst trimfeed to the catalyst system, wherein a molar amount of the secondcatalyst added via the catalyst trim feed per gram of a drycommonly-supported catalyst system ranges from 1.8 μmol to 150 μmol,wherein the first catalyst comprises di(1-ethylindenyl) zirconiumdimethyl having at least one of the following structures:

or di(1-ethylindenyl) zirconium dichloride having one of the structuresabove except that the Me is replaced by Cl, and wherein the secondcatalyst comprises bis(n-propylcyclopentadienyl) hafnium dimethyl havingthe following structure:


2. The method of claim 1, wherein the commonly-supported catalyst systemcomprises at least one catalyst having the following structure:Cp^(A)Cp^(B)MXn, wherein Cp^(A) and Cp^(B) are each independentlyselected from the group consisting of substituted or unsubstitutedcyclopentadienyl, indenyl, tetrahydroindenyl, and fluorenyl compounds;wherein M is chemically bonded to Cp^(A) and Cp^(B) and selected fromthe group consisting of Groups 4, 5, and 6 atoms; wherein each X ischemically bonded to M and is independently selected from the groupconsisting of halogen ions, hydrides, C1 to C12 alkyls, C2 to C12alkenyls, C6 to C12 aryls, C7 to C20 alkylaryls, C1 to C12 alkoxys, C6to C16 aryloxys, C7 to C8 alkylaryloxys, Cl to C12 fluoroalkyls, C6 toC12 fluoroaryls, and C1 to C12 heteroatom-containing hydrocarbons; andwherein n is 0 or an integer from 1 to
 4. 3. The method of claim 1,wherein the commonly-supported catalyst system comprises at least onecatalyst that is a chromium-based catalyst, Ziegler-Natta catalyst, orGroup 15-containing catalyst.
 4. The method of claim 1, wherein thecatalyst trim feed is added to a slurry comprising the first catalyst.5. The method of claim 1, wherein the catalyst trim feed is a solutiontrim feed.
 6. The method of claim 1, wherein the molar amount ofcatalyst added via the catalyst trim feed per gram of the drycommonly-supported catalyst system ranges from 12.4 μmol to 75 μmol. 7.The method of claim 1, wherein the polyolefin polymer is bimodal.
 8. Themethod of claim 1, wherein the commonly-supported catalyst systemcomprises an activator.
 9. The method of claim 8, wherein the activatorcomprises at least one of a methylaluminoxane (MAO) and a silicamethylaluminoxane (SMAO).
 10. The method of claim 1, wherein the initialco-deposit on a mol fraction basis of the second catalyst to the firstcatalyst in the commonly-supported catalyst system ranges from about0.7:0.3 to about 0.3:0.7.
 11. The method of claim 1, wherein the initialco-deposit on a mol fraction basis of the second catalyst to the firstcatalyst in the commonly-supported catalyst system ranges from about0.6:0.4 to about 0.4:0.6.
 12. The method of claim 1, wherein thecomonomer comprises an alpha olefin having from 4 to 20 carbon atoms.13. The method of claim 1, wherein the comonomer comprises butene orhexene.